DHANALAKSHMI COLLEGE OF ENGINEERING
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EE6402 TRANSMISSION AND DISTRIBUTION
UNIT-I – TRANSMISSION SYSTEM – INTRODUCTION
PART A
Structure of electric power system
1. Define – Regional Grid
(N-07)
2. Draw a single line diagram for modern electric power system.
(N-06)
3. What is meant by electric power system?
(M-09)
4. List out the various components of power system.
5. What is meant by primary transmission?
Transmission system
6. Why is high voltage preferred for power transmission lines?
(N-07)
7. What are the advantages of AC transmission system?
8. What are the disadvantages of AC transmission system?
Distribution system
9. List out the advantages of ring main distribution system over radial system.
(M-07)
10. Compare overhead system with underground system.
EHVAC
11. State the advantages of EHVAC transmission system.
(A-08)
12. Define – EHVAC
FACTS
13. List out the various types of devices in FACTS.
(N-08)
14. What is meant by STATCOM?
(M-07)
15. What is the necessity of FACTS?
(A-10)
HVDC transmission system
16. List out the HVDC transmission systems in India.
(N-08)
17. List out the various types of devices in FACTS.
(N-08)
Mechanical design of transmission line between towers-sag and tension calculation
18. Define – Sag
PART B
Structure of electric power system
1. Explain the structure of a modern electric power system with various voltage levels.
(16)
Transmission system
2. Explain the effect of increasing the system voltage on volume of a copper and efficiency of a
transmission line.
(16)
EHVAC
3. Why is the transmission of electric power carried out at high voltage?
(16) (N-08)
4. Compare the HVDC transmission with EHVAC transmission in the following aspects:
a) Economics of Transmission
(8)
b) Reliability
(4)
c) Technical Performance
(4) (M-09)
5. Explain in detail, the necessity, advantages and disadvantages of EHVAC transmission
system
(16)
HVDC transmission system
6. Explain the advantages of HVDC transmission over HVAC transmission system.
(16) (N-08)
7. (i) Describe the various types of HVDC links.
(ii) Explain the main components of a HVDC system.
(8)
(8) (N-06)
8. (i) Compare EHVAC and HVDC transmission.
(ii) Describe the various types of HVDC transmission system.
(8)
(8)
FACTS
1. Explain in detail, the simple model of UPFC with a neat diagram.
2. Explain in detail, the importance of FACTS with a neat diagram.
(16) (N-07)
(16) (N-2006)
3. Explain in detail, the TCSC and the SVC systems.
(16)
4. Explain in detail, the STATCOM and the UPFC with neat diagram.
(16)
UNIT- II – TRANSMISSION LINE PARAMETERS
PART A
Single and double circuits
1. What is the necessity for a double circuit line?
2. What is meant by ACSR conductor?
Strand conductor
3. Distinguish between stranded conductors and bundled conductors.
(N-07)
Bundle conductor
4. List out the advantages of bundled conductors.
(N-08)
Symmetrical Spacing
5. What is meant by symmetrical spacing?
Concepts of GMR and GMD
6. Define – Mutual GMD of a transmission line
7. Define – Self GMD of a transmission line
Skin effect
8. What is meant by skin effect?
(N-08)
Proximity effect
9. What is meant by proximity effect?
(N-07)
10. What is meant by Ferranti effect?
(M-09)
PART B
Parameters of resistance, inductance and capacitance calculation
1. Derive an expression for an inductance of a single phase transmission system.
(16)
2. Find the capacitance per km per phase of a 3Φ line arrangement in a horizontal plane
spaced 8 m apart. The height of all conductors above the earth is 13 m. The diameter of
each conductor is 2.6 cm. the line is completely transposed and takes the effect of ground
into account.
(16)
3. Find the capacitance between the conductors of a single-phase 10 km long line. The
diameter of each conductor is 1.213 cm. The spacing between conductors is 1.25 m. Also
find the capacitance of each conductor neutral.
(16)
4. A 50 km long transmission line supplies a load of 5 MVA at 0.8 pf lagging at 33 kV. The
transmission efficiency is 90%. Calculate the volume of aluminium conductor required for
the transmission line, for the following cases:
a) Single phase, 2 wire
b) 3 phase, 3 wire system
The specific resistance of aluminium is 2.85 x 10-8 Ωm.
(16) (N-08)
Single and double circuits
5.
Derive an expression for the capacitance of a double circuit line with hexagonal spacing. (6)
Bundle conductor
9. Explain the advantages of bundled conductors.
(8)
Symmetrical Spacing
10. Derive an expression for the capacitance of a 3 phase transmission line with equilateral
spacing.
(16) (N-07)
Unsymmetrical Spacing
11. Derive an expression for inductance of a 3 phase transmission line with unsymmetrical
spacing.
(16)
Concepts of GMR and GMD
12. Describe the concept of GMR and GMD in the calculation of transmission line inductance.
(16)
Skin effect
13. Explain in detail, the skin effect with respect to overhead lines.
(8)
Proximity effect
14. Write short notes on proximity effect.
(8) (N-08)
Interference with neighbouring communication lines
15. Write short notes on the inductive interference power and communication lines.
(8)
UNIT-III
MODELLING AND PERFORMANCE OF TRANSMISSION LINES
PART A
Transmission line classification – short line, medium line and long line
1. What is the need for different transmission line models?
(N-06)
2. What is meant by corona?
(M-09)
3. Write the different types of transmission line based on its length.
(A-08)
4. Draw the phasor representation of a short transmission line.
(M-07)
5. Draw the nominal-T representation of a transmission line.
(A-08)
Voltage regulation
6. Define – Regulation of Transmission Line
7. What are different types of the regulating equipments used in transmission system?
Transmission efficiency
8. Define – Transmission Efficiency
Power circle diagrams
9. What is meant by power circle diagram?
(N-08)
Surge impedance loading
10. What is meant by surge impedance?
11. What is meant by surge impedance loading?
(N-08)
PART B
Transmission line classification – short line, medium line and long line
1. Explain in detail, the various factors affecting corona loss.
(16) (N-08)
2. A 3 phase short transmission line has a series line impedance of (20+j50) Ω per phase. The
line delivers a load of 50 MW at 0.7 pf lag. Determine the regulation of the line and the
A,B,C and D parameters of the line. If the same load is delivered at 0.7 pf lead, determine the
regulation of the line. Given the system voltage of 220 kV.
(16) (N-07)
3. Derive the expressions of A B C D parameters of a nominal–π network in a medium
transmission line.
(16) (N-06)
4.
Using nominal–π method, find the sending end voltage and voltage regulation of a 250 km,
3 phase, 50 Hz, transmission line delivering 25 MVA at 0.8 lagging pf to a balanced load at
132 kV. The line conductors are spaced equilaterally 3 m apart. The conductor resistance is
0.11 Ω/km and its effective diameter is 1.6 cm. Neglect leakage reactance.
(16) (N-06)
5. A 15 km long 3 phase overhead transmission line delivers 5 MW at 11 kV at 0.8 lagging pf,
line loss is 12% of power delivered. Line inductance is 1.1 mH per km per phase. Find the
sending end voltage and regulation.
(16) (M-09)
Equivalent circuits
5. Derive an expression for sending end voltage in the nominal T method and the end condenser
method.
(16)
6. Draw the equivalent circuit of nominal–π method of long transmission line? Derive the
expression for parameters of this circuit in terms of line parameters.
(8)
Voltage regulation and Transmission efficiency
7. Explain in detail, the end condenser method for a medium transmission line. (16) (M-09)
8. A three phase 5 km long transmission line, having resistance of 0.5 Ω / km and inductance of
1.76 mH/km is delivering power at 0.8 pf lagging. The receiving end voltage is 32 kV. If the
supply voltage is 33 kV, 50 Hz, find line current, regulation and efficiency of the
transmission line.
(16)
9. Write short notes on regulation of a transmission line. Also derive the approximate
expression for the regulation of a short transmission line.
(16)
UNIT-IV – INSULATORS AND CABLES
PART A
Classificationof insulators for transmission and distribution purpose
1. Write the advantages of polymeric insulators over porcelain insulators.
(N-07)
2. What are the required characteristics of an insulator used in the transmission system? (N-06)
3. Why is the potential distribution across the string units of insulator not uniform?
4. List out the various properties of an insulating material.
(M-07)
(A-10)
5. What is meant by shackle insulator?
6. Write the types of insulators used for overhead transmission line.
7. Write the characteristics of an insulator.
Voltage distribution in insulator string and grading
8. Define – Dielectric Stress
9. Define – Factor of Safety
Improvement of string efficiency
10. What are the various methods of improving the string efficiency in an insulator?
(N-08)
Underground cables
11. What are the different components of resistances in an underground cable?
(N-06)
12. List out the insulating materials used in cables.
(M-09)
PART B
Classificationof insulators for transmission and distribution purpose
1. Derive an expression for insulator resistance, insulator capacitance and electric stress in a
single core cable.
(16)
2. Explain in detail, the pin type insulator with neat diagrams.
(8)
3. A 3 phase overhead transmission line is being supported by three disc insulators. The
potential across top unit (i.e. near the tower) and the middle unit are 8kV and 11kV
respectively. Calculate the following:
a) The ratio of capacitance between pin and earth to the self capacitance of each unit
b) Line Voltage
c) String Efficiency
(16)
Voltage distribution in insulator string and grading
4. (i) What is the need for grading an insulator string?
(ii) Explain in detail, the different methods of grading of an insulator.
5. Write short notes on the following:
a).Capacitance grading
b) Inter-sheath grading
6. Explain the construction of a 3 core belted cable type with a neat diagram.
(8)
(8) (N-06)
(8)
(8) (M-09)
(8)
Improvement of string efficiency
7. Explain any two methods to increase the value of string efficiency, with suitable diagrams.
(16) (N-07)
8. Explain string efficiency. Also calculate its value for a string of three insulator units, if the
capacitance of each unit to earth and line is 20% and 5% of the self capacitance of the unit.
(16) (M-09)
Underground cables
9. Explain in detail, the various methods of grading of cables.
(16)(N-08)
UNIT-V
SUBSTATION GROUNDING SYSTEM AND DISTRIBUTION SYSTEM
PART A
Substation
1. What is meant by substation?
2. What are the different types of substations?
(N-06)
Bus-bar arrangement
3. What is meant by bus-bar?
4. What are the different types of materials used in bus-bars?
Substation schemes- single bus, double bus with double breaker
5. What are the disadvantages of single bus scheme?
(M-07)
6. What is the role of circuit breaker in the power system?
(M-07)
7. What are the functions of a circuit breaker?
(A-08)
Earthing in substation
8. What is meant by earth resistance?
Feeders
9. What is meant by a radial feeder?
(N-06)
10. Define – Feeder
Distributors
11. What are the advantages of ring main distributor?
(M-09)
12. What is meant by interconnected system?
(M-09)
13. Define – Distributor
PART B
Substation
1. Explain in detail, the pole mounted substation with neat diagram.
(16) (N-08)
2. Explain the various types of substations.
(8)
Bus-bar arrangement
3. Explain in detail, the two bus-bar arrangements used in substation with neat diagrams.
(16) (N-08)
4. Write short notes on the following:
a) Bus-bar arrangement in substation
(8)
b) Grounding grids
(8)
Substation schemes- single bus, double bus with double breaker
5. Write short notes on the following:
a) Receiving end power angle diagram
b) Methods of voltage control
c) Different factors affecting corona
(16) (N-06)
Earthing in substation
6. Explain in detail, the need for neutral earthing in a power system.
7. Explain in detail, the different methods of earthing.
(16) (N-06)
(16) (N-06)
Grounding
8. Explain in detail, the different types of grounding system.
9. Explain in detail, the following:
a) Neutral grounding
b) Resistance grounding
(16) (M-2009)
(16)
Feeders
10. Write short notes on the following:
a) Sub mains
b) Stepped and tapered mains
(16)
11. Explain in detail, the design principles of substation grounding system.
(16)
Distributors
12. Write short notes on radial distribution system. Also explain the role of interconnectors in
radial distribution system?
(16) (N-07)